The mobile communication system as a background of the present invention is described below with reference to FIGS. 1 through 4.
FIG. 1 illustrates an example of the system configuration of the mobile communication system relating to the present invention. The cellular mobile communication system configures a service area using a plurality of base station apparatuses.
As illustrated in FIG. 1, the mobile communication system is configures by an upper-level equipment 3, base station apparatuses 1a and 1b subordinate to the upper-level equipment 3, and a mobile terminal 2 interconnected over a mobile telephone network 4. The mobile telephone network 4 is connected to a common public network (or an IP network) 5.
FIGS. 2 and 3 illustrate an image of sector arrangement when a cell of a base station has a sector configuration. A sector is a fan-shaped space circularly expanding around the base station, and can be divided into three 120° sectors, six 60° sectors, etc. FIGS. 2 and 3 respectively illustrate six-sector and three-sector configurations of a sector arrangement image. The base station apparatus is provided with an antenna having the directivity of covering the fan-shaped area of the sector for each sector.
Currently, in the 3GPP (3rd generation partnership project), evolved UTRA and UTRAN relating to a wireless access system and a wireless access network system has been studied as a next generation mobile communication system. In the wireless communication system, the OFDMA is likely to be adopted in the downlink direction.
The OFDMA is a method in which a user can access a transmission line in the OFDMA (orthogonal frequency division multiple) modulation method.
In the OFDMA, a plurality of users share subcarriers, and a high transmission efficiency subcarrier is to be assigned to each user. In this case, it is not common to control each of a number of subcarriers, but a frequency is assigned to a bundle of some consecutive subcarriers. The bundle of subcarriers is referred to as a resource block.
FIG. 4 illustrates a concept of a resource block of the OFDMA. The resource block is obtained by collecting fine subcarriers for 200 kHz through 300 kHz and sectioning them by time. In FIG. 4, the resource blocks sectioned by the same type of line is assigned to the same mobile terminal. The base station apparatus assigns the resource block as the smallest unit in the direction of frequencies and the direction of time. Therefore, the data transmitted in the time unit configures one subframe. The interval in which the subframe is transmitted refers to a TTI (transmission time interval) as a time unit in which data is continuously transmitted at a time.
The base station apparatus transmits the transmission data prepared for each TTI to each mobile terminal. At this time, depending on the amount of data used for each mobile terminal that changes with time, a frequency is assigned to each mobile terminal by the resource block as illustrated in FIG. 4. The assignment control is referred to as scheduling, and the base station apparatus practically controls the assignment.
The following patent document 1 discloses the prior art relating to the assignment of subcarriers in the OFDMA, and the patent documents 2 and 3 disclose the prior art of the mobile communication system having the sector configuration.    Patent Document 1: National Publication of International Patent Application No. 2004-537875    Patent Document 2: Japanese Laid-open Patent Publication No. 2000-286822    Patent Document 3: Japanese Laid-open Patent Publication No. 05-336027